1. Field of the Invention:
The present invention relates to surgical adhesives.
2. Description of the Background:
U.S. Pat. No. 4,740,534 discloses surgical adhesives, which contain NCO-terminated (i.e., containing terminal NCO groups) hydrophilic urethane prepolymers derived from organic polyisocyanates, such as tolylene diisocyanates (TDI) and diphenylmethane diisocyanates (MDI), and hydrophilic polyether polyols of higher oxyethylene content, or combinations thereof with unsaturated cyano compounds containing a cyano group directly bonded to a polymerizable double bond.
Such adhesives, however, in which aromatic polyisocyanates, such as TDI and MDI are used as the starting materials, exhibit toxicity problems, because their hydrolysis products, tolylene diamine and diaminodiphenylmethane, possess a high activity in a microbial mutagenicity test (Ames test). On the other hand, aliphatic or cycloaliphatic polyisocyanates, such as hexamethylene diisocyanate, are of low reactivity and catalysts such as heavy metal compounds and amines are required when these compounds are used as surgical adhesives, and the use of such catalysts causes problems in regard to toxicity.
Thus, there remains a need for surgical adhesives which do not give rise to mutagenic hydrolysis products and do not require the use of toxic catalysts.